Gaseous electric discharge lamp device



July 20,1937.

M. PIRANI' ET AL GASEOUS ELECTRIC'DISCHARGE LAMP DEVICE Filed Oct. e, 1956 mvsm'caas MarceHo Pircm'n Rober'k Rompe Wolfgang Thoure'b Patented July 20, 1937 UNITED STATES I 2,087,735 PATENT OFFICE GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Application October s, 1936, Serial No. 104.312 In Germany October 9, 1935 4 Claims.

The present invention relates to gaseous electric discharge lamp devices generally and more particularly the invention relates to vapor discharge lamps in which the discharge has a high intrinsic brilliancy.

Gaseous electric discharge lamps having a gaseous atmosphere consisting of a fixed gas and the vapor of a vaporizable material, such as mercury, and which operate at vapor pressures considerably higher than 1 atmosphere are now known in the art. The containers of such devices usually consist of an elongated quartz tube and the discharge space is in the nature of a capillary passage through the tube. The distance between the electrodes is approximately mm. or more, which distance is greater than the inner diameter ofthe tube. The electrodes are electron emitting when heated.

The object of the present invention is to provide a gaseous electric discharge device which is capable of operation at vapor pressures exceeding 1 atmosphere and which is simple in structure, is inexpensive to manufacture and which has a long useful operating life. Another object of the invention is to provide a gaseous electric discharge lamp of the above type which is capable of producing light flashes and which is useful in motion picture projection apparatus of the kind having a continuously moving film. Another object of the invention is to provide a long lived, compact, rugged, high heat resisting inexpensively manufactured, and easily activated electrode having high electron emissivity characteristics. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

In accordance with these objects a gaseous electric discharge device embodying the present invention has electrodes consisting of a perforated shell of high melting point material, such as tungsten, containing a mixture of materials, such as a mixture of aluminum oxide, tungsten and an alkaline earth' oxide having high electron emissivity characteristics. The electrodes are centrally mounted in the container of the device and are separated a few millimeters. The container preferably consists of quartz and is tubular or spherical in shape. The inner diameter of the container is several times greater than the distance between the electrodes. The high electron emitting characteristics of the electrodes, the heat resisting quality of its component parts and the great mechanical strength of a gaseous electric discharge lamp device embodying the invention makes possible the operation of the device at vapor pressures considerably greater than one atmosphere and the discharge between said electrodes has a high intrinsic brilliancy. Due to the fact that the electrodes are separated but a few millimeters and the fact that the inner wall of the container is at a distance from the electrodes several times greater than the distance between the electrodes the lamp is particularly suited for operation with a modulated discharge, that is,v the discharge current can be increased momentarily to produce a flash of light. A lamp embodying the present invention is thus particularly useful in motion picture projectors of the type in which the movement of the film is continuous.

In the drawing accompanying andforming part of this specification two embodiments of the invention are shown, in which Fig. 1 is a side elevational, partly sectional view of a gaseous electric discharge lamp embodying the invention,

Fig. 2 is a similar view of another lamp embodying the invention, and

Fig. 3 is a sectional view of an electrode made in accordance with the present invention.

Like numbers denote like parts in all the figures. i

Referring to Fig. 1 of the drawing the gaseous I electric discharge device comprises a tubular quartz container I having two current leads 3 sealed therein, one at each end thereof. Said current leads consist of a' high .melting point material, such as tungsten, and are sealed into said container by means of a graded seal 9. Said container I has a gaseous atmosphere therein consisting of a rare, starting gas, such as argon, neon, or xenon, or a mixture of such gases. A quantity 2 of vaporizable material, such as mercury, is likewise present in said container I. An electrode 4 is mounted on each of said current leads 3 and said electrodes each consist of a hollow body of high melting point material, such as tungsten or molybdenum, having a tubular portion terminating in a conical part which part is welded to the end of the current lead 3 as shown in Fig. 3. The electrodes are separated approximately 2 to 5 mm. and are filled with a mixture 5 of electron emitting materials, preferably a mixture of aluminum oxide, tungsten and the oxide of an alkaline earth. A mixture of 90% aluminum oxide, 9% tungsten and 1% barium oxide or a mixture consisting of 80% aluminum oxide, 10% tungsten and 10% barium oxide is preferred. Each of the electrodes 4 are closed at the end thereof opposite the conical end flanged by a disc 6 (Fig. 3) consisting of the same or similar material as the elec.rode shell. The electrode shell has a plurality of perforations I and are surrounded by mantles 8 which are fastened to the current leads 3. Said mantles 8 consist of high melting point .material, such as quartz, aluminum oxide, tungsten or molybdenum and serve both to intercept sputtered electrode particles and to reduce the radiation of heat from the electrodes 4. A plurality of metal discs iii are welded to the current lead I at a part thereof between the seal 9 and the heat shield 8. Said discs i0 radiate heat to protect the fused joints 9 from excessive heating during the operation of the device. The outer surface of the containeri'has a coating H of heat reflecting material which coating I! has a slit ii therein to permit the light from the discharge between said electrodes 4 to emerge from the lamp. Said reflecting coating l2 assists in maintaining said container l at an elevated temperature during the operation of the device to the end that a higher vapor pressure is present in the container I than would be the case were said coating i2 omitted.

The lamp described aboveis particularly suited for operation with a modulated discharge at high vapor pressures and is therefore useful in connection with motion picture apparatus of the type in which the film moves continually. It will be understood, of course, that many modifications may be made without departure from the invention, for example, the container I may be spherical in shape; a heat insulating sheath, such as asbestos, can be used in place of the mirror coating i2, or the mirror coating l2, the asbestos sheath, the mantleB as well; as the cooling discs in can be omitted when desired. A strong wire mesh or net is used in place of the perforated shell of the electrodes 4, when desired.

When a device suitable for operation with vapor pressures in excess of 20 atmospheres is desired, and when the discharge is not to be modulated by means of momentary current increases the lamp device illustrated in Fig. 2 is preferred. s embodiment-of the invention is similar in all respects to that shown in Fig. 1 with the exception that the container l is elliptical in shape and has a dome-like appendage i3 immediately above the electrodes 4 which appendage l3 has a heat reflecting coating id of silver, for example, and serves as a depositing surface for the sputtered electrode particles from said electrodes 4. When desired, the coating It covers the entire surface of the container i with the exception of a small window located opposite the discharge path between said electrodes l. In this embodiment of the invention the mantles 8 consist of quartz tubes or similar heat resisting material and extend from a point in front of said electrodes back along lead 3 and are fused to the container l. The end of each mantle 8 adjacent the electrode 4 is provided with a flange l5 which serves to guide the discharge and to intercept sputtered particles from said electrodes 4.

The lamp illustrated in Fig. 2 is capable of operation at extremely high vapor pressures and is an intense light source of high intrinsic brilliancy.

While we have shown, and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing "from the spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States, is:-

1. A gaseous electric discharge lamp device comprising a container, electrodes sealed therein, a starting gas therein and a quantity of vaporisable material therein, each of said electrodes comprising a hollow, perforate body of high melting point material containing a mixture of aluminum oxide, tungsten and an oxide insf! terial having high electronemissivity. charac- .terlstics, said electrodes being centrally mounted in said container and being separated a distarlce of from 2 to'd mm., the inner surface of said container being at a distance irom said electrodes greater than the distance between said electrodes.

2. A gaseous electric discharge lamp device I comprising a container, electrodes and electrode leads sealed therein, a starting gas therein and a quantity of vaporizable material therein, each of said electrodes comprising a hollow, perforate body of high melting point material said body comprising a tubular part, anda conical part, one of said electrode leads extending through said tubular part and being welded to the apex of said conical part, said hollow body containing a mixture of aluminum oxide, tungsten and an oxide material having high electron emissivity characteristics, said electrodes being centrally mounted in said container and being separated a distance of from 2 to 5 mm., the inner surface of said container being at a distance from said electrodes greater than the distance between said electrodes.

3. A gaseous electric discharge lamp device comprising a container, electrodes and electrode leads sealed therein, a starting gas therein and a quantity of vaporizable material therein, each of said electrodes comprising a hollow, perforate body of high melting point material said body comprising a tubular part and a conical part, one of said electrode leads extending through said tubular part and being welded to the apex of said conical part, said hollow body containing a mix-- ture of aluminum oxide, tungsten and an oxide material having high electron emissivity characteristics, a shield partially surrounding each of said electrodes, said electrodes being centrally mounted in said container and being separated a distance of from 2 to 5 mm., the inner surface of said container being at a distance from said electrodes greater than the distance between said electrodes.

4. A gaseous electric discharge lamp device comprising a container, electrodes and electrode leads sealed therein, a starting gas therein and a quantity of vaporizable material therein, each of said electrodes comprising a hollow, perforate body of high melting point material said body comprising a tubular part and a conical part. one of said electrode leads extending through said tubular part and being welded'to the apex of said conical part, said hollow body containing a mixture of aluminum oxide, tungsten and an oxide material having high electron emissivity characteristics, said electrodes being centrally mounted in said container and being separated a distance of from 2 to 5 mm., a heat radiator mounted on each of said current leads at a part thereof between said electrodes and said container, the inner surface of said container being at a distance from said electrodes greater than the distance between said electrodes. I

MARCELLO PIRANI. ROBERT ROMPE. WOLFGANG THOURET. 

